1. Field of the Invention
The present invention relates generally to hearing prostheses, and more particularly, to a hearing prosthesis electrode array with a resiliently flexible tip member.
2. Related Art
Electrode arrays, such as cochlear implant electrode arrays, generally consist of a plurality of electrode elements which are adapted to apply electrical stimulation to surrounding tissue to stimulate the surrounding nerves. In cochlear implant applications, the electrode array is implanted within the cochlea of a recipient and applies stimulation to the auditory nerves via a series of electrode elements, in accordance with a set stimulation pattern, controlled by an implanted stimulator unit.
The implanted stimulator unit typically applies the stimulation in a manner which is representative of a detected acoustic signal, such that the stimulation pattern applied by the electrode array stimulates the auditory nerves and elicits a sensation that closely resembles the natural sensation of the detected acoustic signal.
In this regard, it is important that when implanting electrode arrays in sensitive regions of the body, such as the cochlea, that the electrode array be flexible enough to reduce damage to the sensitive structures of the surrounding tissue, and yet be rigid enough to ensure that the general shape and form of the electrode array is maintained during the insertion procedure such that the electrode array can perform as intended.
In electrode arrays of the type used for implantation in the cochlea, it has been found that the tip of the array plays an important role during the insertion procedure. In this regard, there have been attempts to design the tip of the electrode array in a manner that reduces the possibility of the tip of the electrode array from puncturing or abrading the sensitive tissues of the cochlea and causing damage to the nerve structures which the implant is attempting to stimulate.
One such early attempt is described in Australian Patent No. 582264 to Clark et al. This patent discloses the provision of tip or distal end of the electrode array being provided with at least one discontinuity that increases the flexibility of the tip. The tip is generally an extension of the existing electrode array and is made from the same material, but is extending beyond the most distal electrode element.
One problem with such a design is that the tips were typically relatively too flexible such that during the insertion process the tip would catch on the wall of the cochlea and cause the array to bend back on itself, thereby potentially causing more damage to the cochlea than would ordinarily be the case should the flexible tip not be provided. Such a situation can also result in an implant being incorrectly positioned from the auditory nerve potentially reducing the effectiveness of the array in capturing and stimulating the appropriate nerves. Further, such a situation where the array folds upon itself can cause unwanted interaction or shorting between electrode elements that may be touching, thereby reducing the number of electrodes that may be operational for stimulation.
Other designs have also considered providing an extended flexible tip of a lead or electrode array to aid in insertion, such as that described in EP 0 919 254 to Bakels et al. However, as mentioned above, such tips have all been designed with flexibility in mind rather than stability of the tip, hence all suffer from similar problems as identified above.